The present invention relates to a projection type display unit, for example, a liquid crystal projection type display unit, a projection type display device and the like, that projects a reflection on a screen with the use of a light valve such as liquid crystal panels.
Projection type display units include a liquid crystal projection type display unit, a projection type display device and the like in which light from a light source is irradiated on a light valve such as liquid crystal panels, the light valve performs light intensity modulation (also, called spatial light modulation) for transforming into intensity (concentration) of light every pixel, and an optical image is formed, enlarged, and projected onto a screen or the like.
This type of projection type display unit includes therein a plurality of heat generating sources (for example, a lamp of a light source, a light valve, an electric power source for driving the lamp, etc.) and optical parts are shortened in service life due to heat generated from these heat generating sources. Therefore, for example, in the case where the liquid crystal panels are used as a light valve, liquid crystal panels must be kept at temperature of 70° C. or lower. Hereupon, such projection type display unit generally comprises cooling means, by which heat generated from the heat generating sources is exhausted outside the unit.
Conventionally, JP-A-2000-81673 discloses the construction of cooling means for this type of projection type display unit, in which cooling wind paths for cooling a light valve, an electric power source and a light source in the projection type display unit are unified whereby air intake ports and air exhaust ports, respectively, are made in smaller in number than fans used therein to intend to reduce noise leakage outside the projection type display unit from the air intake ports and the air exhaust ports.
Also, JP-A-2002-122839 discloses the construction, in which an intake air by a radial fan is used as a cooling wind in order to cool liquid crystal panels and polarizing plates in a projection type display unit. In this construction, flow of the cooling wind drawn by the radial fan is controlled by guides arranged in a wind path and the cooling wind is concentratedly fed to the liquid crystal panels and the polarizing plates. Since the cooling wind can be efficiently fed to portions that require cooling, a large cooling action can be obtained with low noise.
With the conventional art disclosed in JP-A-2000-81673, however, since cooling wind paths are unified to constitute a single one, heat generating parts, for example, the light valve, the electric power source, the light source, etc. arranged in the cooling wind path from a low-temperature side on sides of the air intake ports to a high-temperature side on sides of the air exhaust ports are restricted in arrangement and it is extremely difficult to have temperatures of respective parts, such as the light valve, the electric power source, the light source, etc. including appropriate margins conformed to the parts. Also, since the light valve, the electric power source and the light source are arranged in the single cooling wind path that is not independent, the electric power source disposed close to the light source is affected by heat of the light source. Further, since the light source is cooled by means of the wind having become hot after cooled the electric power source, a lot of fan air volume is needed to cool the light valve, the electric power source, the light source, etc. and it is difficult to reduce the rotational frequencies of the fans and to reduce noise accompanying the rotation of the fans. Also, since one of the fans is provided close to an air exhaust port opened to a housing, noise generated from the fan is released from the air exhaust port without damping, and so it is difficult to reduce noise.
Also, with the conventional art disclosed in JP-A-2002-122839, an intake air drawn by a radial fan is used to cool the liquid crystal panels and the polarizing plates, and thereafter exhausted from the radial fan passes through a duct as it is and is exhausted from an air exhaust port opened to a housing, and the document does not refer to any use intended for cooling other optical parts. Therefore, the conventional art relates to a technique aiming at low noise and limited to cooling means for a part of elements (for example, liquid crystal panels and polarizing plates) in the projection type display unit, for which cooling is required, and so noise in the entire projection type display unit as well as cooling of other heat generating parts is not necessarily achieved.